//
//  RoseSpec.swift
//  SwiftCheck
//
//  Created by Robert Widmann on 1/24/16.
//  Copyright © 2016 Typelift. All rights reserved.
//

import SwiftCheck
import XCTest
#if SWIFT_PACKAGE
import FileCheck
#endif

class RoseSpec : XCTestCase {
	private static func intRoseTree(_ v : Int) -> Rose<Int> {
		return .mkRose({ v }, { Int.shrink(v).map(intRoseTree) })
	}

	private static func depthOneChildren<A>(_ rose : Rose<A>) -> [A] {
		return rose.children.map { $0.root }
	}

	private static func depthOneAndTwoChildren<A>(_ rose : Rose<A>) -> [A] {
		let topChildren = rose.children
		let vs = topChildren.map { $0.root }
		let cs = topChildren.flatMap({ $0.children }).map({ $0.root })
		return vs + cs
	}

	func testAll() {
		property("Collapse brings up one level of rose tree depth") <- forAll { (i : Int) in
			let tree = RoseSpec.intRoseTree(i)
			return RoseSpec.depthOneChildren(tree.collapse) == RoseSpec.depthOneAndTwoChildren(tree)
		}
	}

	func testLaws() {
		let smallArgs = CheckerArguments(maxTestCaseSize: 5)
		property("Rose obeys the Functor identity law", arguments: smallArgs) <- forAll { (x : RoseTreeOf<Int>) in
			return (x.getRose.map(id)) == id(x.getRose)
		}

		property("Rose obeys the Functor composition law", arguments: smallArgs) <- forAll { (f : ArrowOf<Int, Int>, g : ArrowOf<Int, Int>) in
			return forAll { (x : RoseTreeOf<Int>) in
				return x.getRose.map(f.getArrow • g.getArrow) == x.getRose.map(g.getArrow).map(f.getArrow)
			}
		}

		property("Rose obeys the Applicative identity law", arguments: smallArgs) <- forAll { (x : RoseTreeOf<Int>) in
			return x.getRose.ap(Rose.pure(id)) == x.getRose
		}

		property("Rose obeys the first Applicative composition law", arguments: smallArgs) <- forAll{ (fl : RoseTreeOf<ArrowOf<Int, Int>>, gl : RoseTreeOf<ArrowOf<Int, Int>>, x : RoseTreeOf<Int>) in
			let f = fl.getRose.map({ $0.getArrow })
			let g = gl.getRose.map({ $0.getArrow })
			return x.getRose.ap(g.ap(f.map(curry(•)))) == x.getRose.ap(g).ap(f)
		}

		property("Rose obeys the second Applicative composition law", arguments: smallArgs) <- forAll { (fl : RoseTreeOf<ArrowOf<Int, Int>>, gl : RoseTreeOf<ArrowOf<Int, Int>>, x : RoseTreeOf<Int>) in
			let f = fl.getRose.map({ $0.getArrow })
			let g = gl.getRose.map({ $0.getArrow })
			return x.getRose.ap(g.ap(f.ap(Rose.pure(curry(•))))) == x.getRose.ap(g).ap(f)
		}

		property("Rose obeys the Monad left identity law", arguments: smallArgs) <- forAll { (a : Int, f : ArrowOf<Int, RoseTreeOf<Int>>) in
			return (Rose<Int>.pure(a).flatMap { f.getArrow($0).getRose }) == f.getArrow(a).getRose
		}

		property("Rose obeys the Monad right identity law", arguments: smallArgs) <- forAll { (m : RoseTreeOf<Int>) in
			return m.getRose.flatMap(Rose.pure) == m.getRose
		}

		property("Rose obeys the Monad associativity law", arguments: smallArgs) <- forAll { (f : ArrowOf<Int, RoseTreeOf<Int>>, g : ArrowOf<Int, RoseTreeOf<Int>>) in
			return forAll { (m : RoseTreeOf<Int>) in
				return m.getRose.flatMap({ f.getArrow($0).getRose }).flatMap({ g.getArrow($0).getRose })
						==
						m.getRose.flatMap({ x in f.getArrow(x).getRose.flatMap({ g.getArrow($0).getRose }) })
			}
		}
	}

	#if !(os(macOS) || os(iOS) || os(watchOS) || os(tvOS))
	static var allTests = testCase([
		("testAll", testAll),
		("testLaws", testLaws),
	])
	#endif
}

struct RoseTreeOf<A : Arbitrary> : Arbitrary {
	let getRose : Rose<A>

	init(_ rose : Rose<A>) {
		self.getRose = rose
	}

	static var arbitrary : Gen<RoseTreeOf<A>> {
		return Gen.sized { n in
			return arbTree(n)
		}
	}
}

private func arbTree<A>(_ n : Int) -> Gen<RoseTreeOf<A>> {
	if n == 0 {
		return A.arbitrary.flatMap { Gen.pure(RoseTreeOf(Rose.pure($0))) }
	}
	return Positive<Int>.arbitrary.flatMap { m in
		let n2 = n / (m.getPositive + 1)
		let gg : Gen<(A, [RoseTreeOf<A>])> = Gen<(A, [RoseTreeOf<A>])>.zip(A.arbitrary, arbTree(n2).proliferate(withSize: m.getPositive))
		return gg.map { (t) -> RoseTreeOf<A> in
			let (a, f) = t
			return RoseTreeOf(.mkRose({ a }, { f.map { $0.getRose } }))
		}
	}
}

private func == <T : Equatable>(l : Rose<T>, r : Rose<T>) -> Bool {
	switch (l, r) {
	case let (.mkRose(l1, r1), .mkRose(l2, r2)):
		return l1() == l2() && zip(r1(), r2()).reduce(true) { (a, t) in a && (t.0 == t.1) }
	case (.ioRose(_), .ioRose(_)):
		return true
	default:
		return false
	}
}

extension Rose {
	var root : A {
		switch self.reduce {
		case let .mkRose(root, _):
			return root()
		default:
			fatalError("Rose should not have reduced to .IORose")
		}
	}

	var children : [Rose<A>] {
		switch self.reduce {
		case let .mkRose(_, children):
			return children()
		default:
			fatalError("Rose should not have reduced to .IORose")
		}
	}

	var collapse : Rose<A> {
		let children = self.children

		let vs = children.map { $0.collapse }
		let cs = children.flatMap({ $0.children }).map { $0.collapse }

		return .mkRose({ self.root }, { vs + cs })
	}
}
